Light detecting and ranging (LiDAR) sensors are utilized in a variety of applications to measure the distance to a target, to measure the angle to a target, to determine the location of a target, the speed of a target, the shape of a target, the reflectance of a target, or other target associated parameter. LiDAR sensors are used to collect data about objects without making physical contact with the object. Systems with integrated LiDAR sensors are used extensively to acquire three dimensional geospatial information about a broad range of environments. For example, State Departments of Transportation (DOT) use LiDAR data to measure vertical clearances above roads at overpasses, bridges, and tunnels, as well as to inventory assets such as street signs, traffic lights, lane markings and fire hydrants to cite a few. Commercial mapping companies also use LiDAR to inventory assets such as gas pipelines, electrical transmission lines, to measure material removed from mines, and to map points of interest such as restaurants, parks, or schools located along roadways. LiDAR sensors are especially valuable for detecting objects located within dangerous or hard to access areas, and practicioners have integrated LiDAR sensors into positioning systems mounted in aircraft, on boats, and motor vehicles. Land surveyors have used positioning systems with integrated LiDAR sensors to create topographical maps for their customers.
There are many types of LiDAR sensors. One example of a LIDAR sensor is a Time of Flight based LiDAR sensor. Time of Flight based LiDAR sensors operate by measuring the elapsed time from when a pulse of light is emitted to when the reflected light pulse returns to the sensor. That measurement is known as the Time of Flight (TOF). The light pulse is typically generated by a laser. The reflected pulse is detected by a photoelectric transducer (detector), typically an avalanche photodiode. The measurement of elapsed time is performed by an electronic circuit. By using the formula Distance=(Speed of Light×Time of Flight)/2, a TOF LiDAR sensor can calculate a distance to an object to within one centimeter at ranges greater than 200 meters. Known architectures of LiDAR sensors use one optical path including a dedicated lens to direct outgoing laser pulses towards target surfaces and a second optical path including a separate lens to receive the reflected pulses and direct them towards a detector. Another example of a LiDAR sensor is a phased based LiDAR sensor.
There is a need to provide an improved optical apparatus and method for light detecting and range sensing.